GB2156511A - Optical absorption spectroscopy for semiconductors - Google Patents
Optical absorption spectroscopy for semiconductors Download PDFInfo
- Publication number
- GB2156511A GB2156511A GB08407621A GB8407621A GB2156511A GB 2156511 A GB2156511 A GB 2156511A GB 08407621 A GB08407621 A GB 08407621A GB 8407621 A GB8407621 A GB 8407621A GB 2156511 A GB2156511 A GB 2156511A
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- Prior art keywords
- semiconductor
- layer
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- optical radiation
- semiconductor sample
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- 239000004065 semiconductor Substances 0.000 title claims description 84
- 230000003287 optical effect Effects 0.000 title claims description 50
- 238000004847 absorption spectroscopy Methods 0.000 title description 2
- 238000005253 cladding Methods 0.000 claims description 57
- 238000010521 absorption reaction Methods 0.000 claims description 43
- 230000005855 radiation Effects 0.000 claims description 41
- 239000000758 substrate Substances 0.000 claims description 41
- 238000000034 method Methods 0.000 claims description 29
- 239000000463 material Substances 0.000 claims description 9
- 230000000694 effects Effects 0.000 claims description 6
- 239000003792 electrolyte Substances 0.000 claims description 6
- 239000002800 charge carrier Substances 0.000 claims description 4
- 239000000523 sample Substances 0.000 description 50
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 9
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 8
- 238000001451 molecular beam epitaxy Methods 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000000295 complement effect Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 238000013139 quantization Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/26—Testing of individual semiconductor devices
- G01R31/265—Contactless testing
- G01R31/2656—Contactless testing using non-ionising electromagnetic radiation, e.g. optical radiation
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Electromagnetism (AREA)
- Toxicology (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Testing Or Measuring Of Semiconductors Or The Like (AREA)
Description
1
GB 2 1 56 51 1A 1
SPECIFICATION
Optical absorption spectroscopy for semiconductors
5
This invention relates to a method of spectros-copically analysing optical absorption in a semiconductor sample and further relates to apparatus for use in such a method. 10 Spectroscopic analysis can be used in the evaluation of semiconductor materials for deriving optical absorption data from which various characterising features, for example the relative position of energy levels, can be de-15 termined.
A method of spectroscopically analysing optical absorption in a semiconductor sample is described by D.D. Sell and H.C. Casey Jr. in Journal of Applied Physics, Vol. 45, No. 2, 20 Peb. 1974, pages 800-807. The method described therein includes the steps of providing a layer of the semiconductor sample between two larger band gap semiconductor cladding layers on a substrate. A hole is etched 25 through the substrate and optical radiation is directed via the hole towards the semiconductor sample through the inner cladding layer adjacent the substrate. Radiation which is not absorbed by the semiconductor sample passes 30 through the outer cladding layer and is incident on an external photodetector which thus provides a signal indicative of the absorption in the semiconductor sample.
It is noted that it is radiation transmitted by 35 the sample layer which is actually incident on the photodetector. However, transmission and absorption are complementary parameters, one increasing as the other decreases, the precise relationship between them depending 40 also on interface reflections. Thus while the photodetector senses directly only the transmitted radiation the signal derived therefrom is also indicative of the radiation absorbed by the semiconductor sample. 45 A drawback with the method described in the above journal reference is the requirement to form a hole in the substrate, which is a difficult step and can be very time consuming. For example with a substrate which is 200jum 50 thick it could take as long as half a day to provide a hole through the full thickness of the substrate using conventional polishing and chemical etching techniques.
According to a first aspect of the present 55 invention there is provided a method of spectroscopically analysing optical absorption in a semiconductor sample including the steps of providing a layer of the semiconductor sample between two semiconductor cladding layers 60 on a substrate, which cladding layers have a larger band gap than said semiconductor sample, and directing optical radiation towards said semiconductor sample through one of said cladding layers, characterised in that the 65 semiconductor sample and the cladding layers are of one conductivity type and in that the substrate comprises a semiconductor material of the opposite conductivity type, a p-n junction being present between the substrate and the adjacent cladding layer, which p-n junction is sensitive to optical radiation at a wavelength above the absorption edges of both cladding layers, the method further including the steps of providing first electrode means on the substrate, providing on the outer cladding layer second electrode means transparent to said optical radiation, directing the optical radiation towards the semiconductor sample through said transparent second electrode means, and deriving from the first and second electrode means a signal related to the voltage generated across said p-n junction as a result of the photovoltaic effect, said signal being indicative of the absorption in said semiconductor sample of incident optical radiation in the wavelength range above the absorption edges of the cladding layers and below the wavelength limit at which the p-n junction in sensitive, wherein the outer cladding layer is sufficiently thick to prevent the depletion layer associated with the junction between said outer cladding layer and said second electrode means extending into the semiconductor sample layer, and the inner cladding layer adjacent the substrate is sufficiently thick substantially to confine charge carriers generated by absorption of the optical radiation in the semiconductor sample.
It is noted here that the term "absorption edge" as used herein refers to the wavelength value at which the absorption shows a sudden decrease in value.
Moreover, because of the complementary relationship between transmission and absorption discussed previously in the context of the prior art, it is also noted that the signal derived from the electrode means is indicative of the radiation absorbed by the semiconductor sample although it is the transmitted radiation which is actually sensed by the p-n junction.
A method of spectroscopically analysing optical absorption in a semiconductor sample in accordance with the invention has the advantage that, as compared with the known method mentioned previously, it dispenses with the difficult step of etching a hole in the substrate and in practice this can represent a significant time saving.
In order to optimise the quality of the cladding layers and the semiconductor sample which may be provided on the substrate by known semiconductor growth techniques such as for example molecular beam epitaxy (MBE) it may be preferable to include a buffer layer intermediate the substrate and the inner cladding layer.
The buffer layer may be of the same conductivity type as the semiconductor ssmple and the cladding layers, in which case the p-n
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junction is formed at the interface of the buffer layer and the substrate. Alternatively, the buffer layer may be of the same conductivity type as the substrate, in which case the 5 p-n junction is formed at the interface of the buffer layer and the inner cladding layer. In both cases the buffer layer should have a narrower band gap than the semiconductor sample.
10 The method may be used for deriving the optical absorption data for a semiconductor sample in the form of a conventional semiconductor layer. However, it is equally suitable for deriving optical absorption data for a so-15 called superlattice structure where the sample comprises a periodic arrangement of very thin sub-layers of one semiconductor material interleaved with sub-layers of a different semiconductor material. In a superlattice structure 20 the component layers are so thin that quantization occurs and new discrete energy levels (quantum levels) are created therein. In this case it is to be noted that the cladding layers are regarded as having a larger band gap than 25 the superlattice sample when the band gap of the cladding layers is greater than the energy separation of the new quantum levels in the superlattice sample.
According to a further aspect of the inven-30 tion there is provided apparatus for performing a method of spectroscopically analysing optical absorption in a semiconductor sample in accordance with the first aspect of the invention, wherein the semiconductor sample 35 is provided as a layer of one conductivity type between two larger band gap semiconductor cladding layers of the same conductivity type on an opposite conductivity type semiconductor substrate, a p-n junction being present 40 between the substrate and the adjacent cladding layer, characterised in that the apparatus comprises first electrode means for contacting the substrate, second electrode means transparent to optical radiation for contacting the 45 outer cladding layer, a monochromatic optical radiation source for directing optical radiation towards the semiconductor sample through the transparent electrode means, and means for deriving from the first and second elec-50 trode means a signal related to the voltage generated across the p-n junction as a result of the photovoltaic effect, said signal being indicative of the absorption in said semiconductor sample of the incident optical radia-55 tion.
This apparatus has the advantage that it does not itself include a separate photodetector because the detector is, in effect, the p-n junction between the semiconductor substrate 60 and the adjacent cladding layer.
In order to be able to characterise the semiconductor sample fully it is preferable for the radiation source to have means for varying in a substantially continuous manner the 65 wavelength of the optical radiation emitted.
The apparatus may also comprise means such as a graph plotter for recording the signal derived from the electrode means as a function of the wavelength of the incident optical radiation.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which:
Figure 1 is a part cross-section and a part schematic view of apparatus for deriving optical absorption data for a semiconductor sample using a method in accordance with the invention.
Figure 2 is a graph showing the optical absorption characteristic of a semiconductor sample obtained using this method, and
Figure 3 is an energy band diagram for the various semiconductor layers used in the method.
It is noted that, for the sake of clarity and simplicity, the Figures are largely schematic and not to scale.
The following embodiment is concerned with deriving optical absorption data for a p-type semiconductor sample. As shown in Figure 1, a layer 4 of the semiconductor sample is provided between two p-type semiconductor cladding layers 3,5 on an n-type semiconductor substrate 1. A p-type semiconductor buffer layer is also provided intermediate the substrate 1 and the adjacent cladding layer 3 forming a p-n junction 8 at the interface between the substrate 1 and the buffer layer 2. The provision of these various semiconductor layers is described in more detail below.
The starting material is an n-type gallium arsenide (GaAs) substrate 1 which is doped with an impurity concentration of 1018cm~3. The substrate 1 may, for example, be 10mm square and have a thickness of approximately 300/im. A 0.2jum thick buffer layer 2 of p-type GaAs is grown on the substrate 1 using molecular beam epitaxy (MBE). The buffer layer 2 is not intentionally doped but has an effective impurity concentration of 2 X 1016cm-3. The p-n junction 8 is thus formed at the interface between the substrate
1 and the buffer layer 2.
Next a 0.5pm thick cladding layer 3 of p-type Al05Ga05As is grown by MBE on the buffer layer 2. Cladding layer 3 is not intentionally doped but has an effective impurity concentration of approximately 2 X 1016cm~3. The semiconductor sample of interest is then provided as a p-type layer 4 on the cladding layer 3 and a further 0.5jum thick cladding layer 5 of p-type AI06Ga05As is grown by MBE on layer 4. Again, the layers 4 and 5 are not intentionally doped but have an effective impurity concentration of approximately
2 X 1016cm 3. In the present embodiment the semiconductor sample is a so-called 'superlattice' structure comprising a periodic arrangement of alternate AI05Ga05As and GaAs sublayers grown by MBE. MBE is known to
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GB 2 1 56 511A
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produce atomically smooth layers and to allow very precise control over layer thicknesses. The overall thickness of the sample layer 4 is 3/im comprising 100 periods. The Alo5Ga05As 5 layers are approximately 200 angstroms thick and the GaAs layers are approximately 100 angstroms thick. The component layers of this superlattice structure are so thin, that quantization occurs and new discrete energy levels 10 are created in the GaAs layers as described in more detail below with reference to Figure 3. Incident photons can be absorbed by the sample layer 4 when the photon energy is greater than or equal to the energy associated 15 with the absorption edge of the sample layer 4. Thus, by deriving optical absorption data for the superlattice layer 4 the energy of the absorbed photons can be established and hence it is possible to determine where the 20 new energy levels occur.
Having grown the semiconductor layer configuration described above the method can proceed as follows.
Electrical contact is made to the substrate 1 25 by a metal probe 7 and to the outer cladding layer 5 by an electrolyte 8. The electrolyte, which may be sodium hydroxide for example, is contained in a cylindrical vessel 9 approximately 1 mm in diameter and centrally dis-30 posed on the cladding layer 5. The electrolyte 8 and the probe 7 are connected to a graph plotter 11 for recording the electric signal generated in the external circuitry. Although not shown in the drawing the apparatus 35 suitably would further include means, such as a chopper, for modulating the incident radiation, and a synchronous detection facility to improve the signal to noise ratio.
Monochromatic optical radiation (repre-40 sented by the arrow in Figure 1) from a monochromator 10 is directed towards the semiconductor sample through the transparent electrolyte 8. The absorption edge of Al-05Ga05As occurs at approximately 600nm. 45 Thus for optical radiation having a wavelength greater than 600nm the outer cladding layers 3 and 5 are transparent. Thus, unless the radiation is absorbed by the sample layer 4 it is transmitted to the GaAs buffer layer 2 50 adjacent the p-n junction 6. The absorption edge of GaAs occurs at approximately 880nm so that shorter wavelength radiation reaching the buffer layer 2 produces electron-hole pairs in the depletion region around the p-n 55 jucntion 6. A forward voltage is thus developed across the p-n junction 6 as a result of the photovoltaic effect. Consequently an electric signal is generated in the external circuit. Because of the complementary relationship 60 between absorption and transmission the electric signal thus derived is indicative of absorption in the semiconductor sample layer 4, although it is transmitted radiation which is actually sensed by the p-n junction 6. The 65 electric signal is recorded on a graph plotter
11 as a function of the wavelength of the incident optical radiation. Figure 2 shows the graph thus obtained for the superlattice sample described above. Optical absorption information is available in the wavelength range 600 to 880nm as discussed previously. The troughs in the curve represent a high degree of absorption, i.e. a low level of transmission, in layer 4. With the superlattice structure described the Applicants have found major absorption features occuring at approximately 850nm and 800nm attributable to the quantum levels n = 1 and n = 2 respectively. This suggests that the energy separation of the n = 1 quantum levels of the superlattice layer 4 is 1.46eV and 1.55 eV for the n = 2 quantum levels. This should be compared with the conventional band gap values of 1.42eV for bulk GaAs and 2eV for bulk AloSGao5As.
Figure 3 shows the energy band diagram for the semiconductor layer configuration described above. It is noted that the outer cladding layer 5 is sufficiently thick that band bending in the vicinity of the junction with the electrolyte 8 is confined to layer 5. In other words the depletion layer associated with that junction is prevented from extending through layer 5 to the sample layer 4. The sample layer 4 has a potential well associated with each of the thin GaAs component layers and the energy separation of the new quantum levels n = 1 and n = 2 is represented by the arrows labelled E(n = 1) and E(n = 2) respectively. The band gap of both the outer cladding layer 5 and the inner cladding layer 3 is greater than the energy separation of the new quantum levels in the sample layer 4. The inner clading layer 3 is sufficiently thick to confine charge carriers generated by absorption of the optical radiation in the potential well, that is to say in the semiconductor sample layer 4. Thus these photogenerated charge carriers cannot contribute to the voltage developed across the p-n junction 6.
It will be evident in view of the exposition of the invention so far that various modifications may be made within the scope of the invention. For example the method can equally well be used for deriving optical absorption data for a conventional semiconductor layer rather than a superlattice structure. Also it may in some circumstances be permissible to dispense with the buffer layer which is provided primarily to improve the quality of the layers grown epitaxially thereon. In that case the p-n junction is formed at the interface between the substrate and the inner cladding layer. Alternatively, the buffer layer may be of the same conductivity type as the substrate in which case the p-n junction is formed at the interface of the inner cladding layer and the buffer layer. As another modification it is possible for the cladding layers to comprise different semiconductor materials
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GB 2 156 511A 4
with different band gaps. It is then possible to observe absorption features in the wavelength range above the absorption edges of both cladding layers and below the wavelength 5 limit at which the p-n junction is sensitive. Finally, it is noted that the conductivity type of all the semiconductor materials may be of the opposite conductivity type. Thus it is possible to measure the optical absorption of 10 an n-type semiconductor sample layer between two n-type cladding layers on a p-type substrate.
Claims (12)
15 1. A method of spectroscopically analysing optical absorption in a semiconductor sample including the steps of providing a layer of the semiconductor sample between two semiconductor cladding layers on a substrate, which 20 cladding layers have a larger band gap than said semiconductor sample, and directing optical radiation towards said semiconductor sample through one of said cladding layers, characterised in that the semiconductor sam-25 pie and the cladding layers are of one conductivity type and in that the substrate comprises a semiconductor material of the opposite conductivity type, a p-n junction being present between the substrate and the adjacent ciadd-30 ing layer, which p-n junction is sensitive to optical radiation at a wavelength above the absorption edges of both cladding layers, the method further including the steps of providing first electrode means on the substrate, 35 providing on the outer cladding layer second electrode means transparent to said optical radiation, directing the optical radiation towards the semiconductor sample through said transparent second electrode means, and de-40 riving from the first and second electrode means a signal related to the voltsge generated across said p-n junction as a result of the photovoltaic effect, said signal being indicative of the absorption in said semiconductor 45 sample of incident optical radiation in the wavelength range above the absorption edges of the cladding layers and below the wavelength limit at which the p-n junction in sensitive, wherein the outer cladding layer is 50 sufficiently thick to prevent the depletion layer associated with the junction between said outer cladding layer and said second electrode means extending into the semiconductor sample layer, and the inner cladding layer adja-55 cent the substrate is sufficiently thick substantially to confine charge carriers generated by absorption of the optical radiation in the semiconductor sample.
2. A method as claimed in Claim 1, charac-60 terised by the further step of providing a semiconductor buffer layer intermediate the substrate and the inner cladding layer.
3. A method as claimed in Claim 2, characterised in that the buffer layer comprises ma-
65 terial of the same conductivity type as the semiconductor sample and the cladding layers, whereby the p-n junction is present at the interface of the buffer layer and the substrate.
4. A method as claimed in any of the preceding claims, characterised in that the cladding layers comprise the same semiconductor material.
5. A method as claimed in any of the preceding Claims, chracterised in that the transparent second electrode means comprises an electrolyte.
6. A method as claimed in any of the preceding Claims, characterised in that the semiconductor sample layer comprises sublayers of different semiconductor materials.
7. A method as claimed in any of the preceding claims, characterised by the further step of varying the wavelength of the incident optical radiation, and recording the signal derived from the electrode means as a function of said wavelength.
8. A method of spectroscopically analysing a semiconductor sample substantially as herein described with reference to Figures 1 and 2 of the accompanying drawing.
9. Apparatus for performing a method of spectroscopically analysing optical absorption in a semiconductor sample as claimed in any of the preceding claims, wherein the semiconductor sample is provided as a layer of one conductivity type between two larger band gap semiconductor cladding layers of the same conductivity type on an opposite conductivity type semiconductor substrate, a p-n junction being present between the substrate and the adjacent cladding layer, characterised in that the apparatus comprises first electrode means for contacting the substrate, second electrode means transparent to optical radiation for contacting the outer cladding layer, a monochromatic optical radiation source for directing optical radiation towards the semiconductor sample through the transparent electrode means, and means for deriving from the first and second electrode means a signal related to the voltage generated across the p-n junction as a result of the photovoltaic effect, said signal being indicative of the absorption in said semiconductor sample of the incident optical radiation.
10. Apparatus as claimed in Claim 9, characterised in that the radiation source has means for varying the wavelength of optical radiation emitted.
11. Apparatus as claimed in Claim 10, characterised in that means are included for recording the signal derived from the electrode means as a function of the wavelength of the incident optical radiation.
12. Apparatus for performing a method of spectroscopically analysing optical absorption in a semiconductor sample substantially as herein described with reference to Figure 1 of the accompanying drawing.
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5
GB 2156 511A 5
Printed in the United Kingdom for
Her Majesty's Stationery Office, Dd 8818935, 1985, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08407621A GB2156511A (en) | 1984-03-23 | 1984-03-23 | Optical absorption spectroscopy for semiconductors |
| US06/713,525 US4678989A (en) | 1984-03-23 | 1985-03-19 | Optical absorption spectroscopy for semiconductors |
| EP85200429A EP0155744B1 (en) | 1984-03-23 | 1985-03-20 | Optical absorption spectroscopy for semiconductors |
| JP60054697A JPS60213043A (en) | 1984-03-23 | 1985-03-20 | Method and device for spectrally analyzing optical absorption of semiconductor material |
| DE8585200429T DE3576411D1 (en) | 1984-03-23 | 1985-03-20 | METHOD FOR OPTICAL ABSORPTION SPECTROSCOPY IN SEMICONDUCTORS. |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08407621A GB2156511A (en) | 1984-03-23 | 1984-03-23 | Optical absorption spectroscopy for semiconductors |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8407621D0 GB8407621D0 (en) | 1984-05-02 |
| GB2156511A true GB2156511A (en) | 1985-10-09 |
Family
ID=10558596
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08407621A Withdrawn GB2156511A (en) | 1984-03-23 | 1984-03-23 | Optical absorption spectroscopy for semiconductors |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4678989A (en) |
| EP (1) | EP0155744B1 (en) |
| JP (1) | JPS60213043A (en) |
| DE (1) | DE3576411D1 (en) |
| GB (1) | GB2156511A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5200693A (en) * | 1991-02-26 | 1993-04-06 | Cornell Research Foundation, Inc. | Method for determining characteristics of pn semiconductor structures |
| US8130203B2 (en) * | 2007-01-03 | 2012-03-06 | Apple Inc. | Multi-touch input discrimination |
| JP5319318B2 (en) | 2009-02-02 | 2013-10-16 | アイダエンジニアリング株式会社 | Motor drive control device |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3982207A (en) * | 1975-03-07 | 1976-09-21 | Bell Telephone Laboratories, Incorporated | Quantum effects in heterostructure lasers |
| US4218143A (en) * | 1979-01-22 | 1980-08-19 | The United States Of America As Represented By The Secretary Of The Navy | Lattice matching measurement device |
| DE2924079A1 (en) * | 1979-06-15 | 1980-12-18 | Varta Batterie | Secondary cell charged by light incidence - with PN junction acting as integrated photocell |
| US4278474A (en) * | 1980-03-25 | 1981-07-14 | The United States Of America As Represented By The United States Department Of Energy | Device for conversion of electromagnetic radiation into electrical current |
| DE3116611C2 (en) * | 1980-05-01 | 1985-05-15 | Hitachi, Ltd., Tokio/Tokyo | Device for measuring semiconductor properties |
| US4333051A (en) * | 1980-05-28 | 1982-06-01 | Rca Corporation | Method and apparatus for determining minority carrier diffusion length in semiconductors |
| US4438446A (en) * | 1981-05-29 | 1984-03-20 | Bell Telephone Laboratories, Incorporated | Double barrier double heterostructure laser |
| US4433288A (en) * | 1981-07-06 | 1984-02-21 | Rca Corporation | Method and apparatus for determining minority carrier diffusion length in semiconductors |
| US4473795A (en) * | 1983-02-23 | 1984-09-25 | International Business Machines Corporation | System for resist defect measurement |
-
1984
- 1984-03-23 GB GB08407621A patent/GB2156511A/en not_active Withdrawn
-
1985
- 1985-03-19 US US06/713,525 patent/US4678989A/en not_active Expired - Fee Related
- 1985-03-20 JP JP60054697A patent/JPS60213043A/en active Pending
- 1985-03-20 DE DE8585200429T patent/DE3576411D1/en not_active Expired - Lifetime
- 1985-03-20 EP EP85200429A patent/EP0155744B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0155744B1 (en) | 1990-03-07 |
| DE3576411D1 (en) | 1990-04-12 |
| EP0155744A3 (en) | 1986-10-29 |
| JPS60213043A (en) | 1985-10-25 |
| GB8407621D0 (en) | 1984-05-02 |
| EP0155744A2 (en) | 1985-09-25 |
| US4678989A (en) | 1987-07-07 |
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| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |